In a companion application filed by the inventors, there is claimed a method for ablation of tissue in the esophagus using a cryogenic gas. In a specific therapeutic application, Barrett's esophagus is treated, although other intestinal lesions may also be treated. While the therapeutic treatment is effective, the cold cryogenic gas tends to make the catheter stiff and unmanageable, and at times rupturing the catheter. The herein disclosed invention is designed to remedy the problem of catheter stiffening. The inventors have solved this problem by a system by which the catheter is heated and its flexibility maintained during cryogenic surgery. Besides the issue of catheter flexibility, the heated catheter is intended to eliminate the freezing of the catheter to the lumen of an endoscope. Heating of the catheter will prevent ice formation which causes sticking.
Prior Art U.S. Patents
Crockett (U.S. Pat. No. 5,800,488) teaches a cryoprobe with a warming feature. The warming feature allows for the quick removal of the probe after cryosurgery. Crockett does not teach the concept of an electrically heated catheter.
Chang et al (U.S. Pat. No. 5,400,602) teaches a cryogenic transport hose designed facilitate the supply and return of cryogenic fluid such as a liquefied gas. Flexibility of the hose's maintained by using multiple layers of reflective metallized material, surrounded by a layer of foam material which, in turn, is surrounded on outer cover all covering the gas supply. An electric means for heating the transport hose is not shown by Chang et al.
Lee (U.S. Pat. No. 3,298,371) teaches a cryogenic probe useful in neurosurgery. The Lee patent also teaches an electric means for heating the exterior of the probe. This heating means is provided in the event the insulation on the exterior of the probe is inadequate to thermally isolate non-target tissue surrounding the probe. In this way, non-target areas will not be affected by the cold, and only the cold probe tip will be presented to the target area. While Lee discloses an external heating means, the reference is silent as to teaching externally heating a catheter which is to be used to convey a gas during a cryosurgical procedure.
Barken (U.S. Pat. No. 5,531,742) teaches a computer controlled cryosurgery apparatus. No electrical catheter heating means is shown by Barken.
Thomas (U.S. Pat. No. 3,507,283) discloses a cryosurgical probe whose temperature is precisely controlled to a desired heat or cold level. Thomas employs heating wire along the external surface of the instrument. Also shown is a cover of heat shrinkable polytetrafluoroethylene to protect the user's hand from the cold. This patent does not disclose the heating of a catheter which is to be used during cryosurgery in which a gas is to be applied during cryoablation.
Griswold (U.S. Pat. No. 5,658,276) teaches a heated cryosurgical probe with a heated exterior which is able to release a frozen probe from cryoablated tissue so that areas of the body not being treated by the probe are not damaged by the cold instrument. The heat is produced by a battery-energized external surface of the probe. Griswold does not teach a heated catheter used to spray a cryogas during internal cryosurgery.